[adrianratnapala]

Looking at this map (http://www.freeworldmaps.net/africa/africa-physical-map.jpg) I see that nearly all the stright-line borders in Africa are in deserts.

Dividing geography with existing populations and long histories into discrete countries is always going to produce tricky ethnic issues. It's just that in Europe those issues were worked out violently over a period of centuries up to and including the second world war. The process is so big, that people don't notice it.